1. Field of the Invention:
The present invention relates to the manufacture of filter media for application in locomotive lubrication oil systems. The present invention also relates to the filtration of locomotive lubricating oil employing such filter media.
2. Description of the Prior Art:
Railroad locomotive lube oil filters must meet certain physical characteristics in order to perform adequately and overcome the problem often encountered with water getting into the lube oil. The problem of water in the lube oil is a very common and serious problem if one does not use an appropriate lube oil filter in the locomotive engine. The result of using an inappropriate filter is that the water softens and swells the filter, the filter becomes very limp and the bottom edge of the pleat extrudes into the center tube of the filter, thereby causing blockage of the line or at least a decrease in flow rate i.e., high pressure drop. In order to test filter materials to determine whether they would be appropriate for use in locomotive engines, a water extrusion resistance test has been formulated in order to test the water extrusion resistance of the filter medium. In the test, one first tests the flow resistance of the filter paper to lube oil at a certain temperature and flow rate. Then, the paper is tested for flow resistance against a water-in-oil emulsion (generally about 1% water in oil emulsion) at the same temperature and flow rate. A ratio of the respective pressures measured, i.e., pressure at X gpm of emulsion/pressure at X gpm of lube oil, is indicative of the suitability of the filter media. The industry generally considers anything over about 1.1 as generally not suitable for application in locomotive lube oil filters.
Due to the problem of water often appearing in the locomotive lube oil, to date the industry has adopted the use of a one side coated filter paper made of cotton linter fibers. The filter used is essentially that described in U.S. Pat. No. 3,116,245 issued to Robert W. McNabb and Howard L. Dahlstrom. The use of cotton linter fibers results in a filter medium exhibiting good resistance to water extrusion and good filtration characteristics. The problem with using cotton as a source, however, is the cyclical variance in supply. Even when cotton is available, the price is prohibitive, e.g., $1200/ton, as compared to other wood pulps, such as the Kraft wood pulps, which average about $300/ton. The use of Kraft pulp in filter media for application in the filtering of locomotive lube oil is unsuitable, however, as the filter medium can exhibit poor-resistance to water extrusion. To provide a filter media which replaces at least a substantial part of the cotton generally used would be of benefit to the industry, providing the filter medium can perform adequately as a locomotive lube oil filter, i.e., exhibit adequate water extrusion resistance.
Accordingly, it is an object of the present invention to provide filter media for use in the filtering of locomotive lube oil which comprises a substantial portion of fibers other than cotton fibers.
It is yet another object of the present invention to provide such filter media which exhibit good filtering characteristics and improved filtration capacity.
It is still another object of the present invention to provide such filter media which is much less expensive than filter media made from substantially all cotton linter fibers.
Another object of the present invention is to provide a process for filtering locomotive lube oil employing such filter media.
These and other objects, as well as the scope, nature and utilization of the invention, will be apparent to those skilled in the art from the following description and the appended claims.